Abstract
The influence of carbon fiber on the statistical life of resin-impregnated carbon fiber reinforced thermoplastic epoxy (CF/TPEP) strands under cyclic tension loading is evaluated using our developed accelerated testing methodology (ATM) based on the time–temperature superposition principle which holds for matrix resin viscoelasticity. First, the formulation of fatigue strength used for this study is introduced. Second, the parameters in the formulation are inferred based on results of viscoelasticity tests of resin, static, and fatigue tensile tests of CF/TPEP strands. Finally, long-term fatigue life prediction for CF/TPEP strands of two kinds is performed using the inferred parameters. Results show that the fatigue strengths of both CF/TPEP strands decrease markedly with an increasing number of cycles to failure and temperature. The S–N master curve is definable and obtained from measured static and fatigue strengths and viscoelastic properties of matrix resin. The S–N master curve for T700/TPEP strand decreases remarkably with increasing Nf compared to that for T300/TPEP strand. Results clarified that the T700/TPEP strand fatigue strength achieved using high strength carbon fiber was lower than that of T300/TPEP strands in the long failure time region.
